Biological processes, anaerobic, aerobic and anoxic are widely used in the treatment of wastewater, however, in most plants applying various treatments two or more tanks are used separately, one for aerobic process and one for anaerobic process, which involves the use of a large area of land.
In the market is known a tank for the wastewater treatment, which removes the organic compounds by a biological treatment of a first anaerobic stage in a lower zone and a second aerobic stage in the upper zone. This tank known as UBOX® is a reactor having two sections: the lower part comprises an anaerobic section, and the upper part an aerobic section. The wastewater is fed into the lower section which is pre-treated anaerobically, using the upflow anaerobic process UASB (Upflow Anaerobic Sludge Bed); the middle section comprises a separation module in three phases to collect and separate the produced biogas and also functioning to maintain the sludge in the bottom of the reactor; on the gas separation and collection module is disposed a plurality of air nozzles through which air is introduced to improve the aerobic degradation of the remaining OCD (Oxygen Chemical Demand). An efficient separator in the upper part of the tank allows the effluent discharge and prevents the exit of the activated sludge, while preventing air bubbles interfere with the sedimentation process.
UBOX® system combines the two processes in a single tank, using an aerobic process in the upper part; but requires aerators, which means high energy consumption and the removal of the organic load is not as efficient, so that sanitation is not the optimal.
In the prior art was found the U.S. Pat. No. 4,692,241 to John L. Nicholson dated on Sep. 8, 1987 which discloses biological rotors for wastewater treatment; in this patent is disclosed in FIG. 1 a lower sedimentation tank 10 with a biozone 20 and a final sedimentation tank 30. The sedimentation tank 10 is an anaerobic zone where sedimentation, sludge accumulation and digestion thereof occurs, after that slightly above there is a transition zone and at the upper part is the biozone or ventilation zone 20 comprising a cover or lid 21 located at the upper part of the lower sedimentation tank 10 and housing a biological contact rotor 22, the rotor has a shaft 25 which is rotated by a motor 23; the biological rotor surface is covered with a thin layer of biomass which is often exposed to the atmosphere while the rotor rotates. Microorganisms that naturally occur in the wastewater feed multiply very rapidly in cyclic periods submerged and exposed to which they are subjected in the rotor surface. The microorganisms decompose rapidly biomass layers.
Water is fed through an opening of the cover or lid 21 which protects the upper part of the biological rotor, and water at the end of the travel through the biological rotor is finally passed to the final sedimentation tank 30 or clarifier tank, where there is less sedimentation and wherein said tank 30 comprises means for recirculating the biomass or sludge from said tank 30 to the tank 10.
In this patent, the tank does not include means for separate a completely anaerobic zone by a separator system from the transition or anoxic zone and which allows the biogas and scum collection from the anaerobic zone and the sludge from the transition or anoxic zone.
U.S. Pat. No. 7,156,986 B2 to Theodore U. Warrow dated on Jan. 2, 2007 was found, which protects a rotating biological contactor, which comprises a first deep clarifier tank 12 where a sedimentation takes place and there is an anaerobic digestion; the tank comprises a semicircular cover on the upper part that separates an anaerobic zone from an aerobic zone, the area above said cover (see FIG. 2) defines a ventilation area where the rotor is driven; the tank comprises an inlet 14 where the wastewater to be treated is discharged and where sedimentation takes place; the clarified water and from which sludge and sediments were removed, is passed through a inlet (see FIG. 3) to the ventilation upper part, where aerobic bacteria have action and the rotor assists in aeration and ventilation to favor the bacterial growth and that they can digest the organic load; this tank presents an anaerobic process and an aerobic process; the water passes through the rotor circuit which is divided into 4 stages where pass the water and at the end is discharged into a clarifier tank.
Like the earlier patent, it is not disclosed or suggested an additional separator of the purely anaerobic zone, or a biogas recovery system that allows collecting and recovering the gas for reuse; nor disclosed or suggested a scum collection system or sludge collecting from the additional transition zone.
It also found the U.S. Pat. No. 7,077,959 B2 to Richard J. Petrone dated on Jul. 18, 2006, which protects a unit of wastewater treatment comprising an inlet 11 to a completely sealed tank 12; in the upper part comprises a reservoir 20 separated from the tank 12 by a bottom wall; in such reservoir a rotary digester 24 is disposed. A second upper reservoir 22 as clarifier unit is disposed in the upper part of the tank; the tank 12 comprises a partitioning wall 46 which divides it into two tanks, the collection tank 13 where the solid are precipitated and in presence of anaerobic bacteria allows a preliminary digestion of organic matter. A secondary tank 15 attached to the tank 13 and separated by the wall 46 receives by decantation the water from the tank 13 and the water in said tank 15 is fed to the reservoir 20 where the rotary digester is disposed, which is immersed 30 to 50% of its diameter where digestion of organic matter in an aerobic process is accelerated; the water after passing through the biological digester pass to the clarifier reservoir 22 and if still found sediment, they are pumped into the tank 13. The clarified and purified water is passed through a disinfection base 56 with UV rays from UV bulbs 54; the UV light destroys microscopic residual microorganisms; alternatively a disinfection bulb or chlorination unit is used.
This tank is divided into two tanks by means of a partitioning wall and a third tank is required to complete the process. Like the earlier patent, it is not disclosed or suggested an additional separator of the purely anaerobic zone, or a biogas recovery system that allows collecting and recovering the gas for reuse; nor disclosed or suggested a scum collection system or sludge collecting from the additional transition zone.
U.S. Pat. No. 5,395,529 to James P. J. Butler dated on 7 Mar. 1995, was found, which discloses an apparatus for wastewater treatment, consisting of a tank comprising an input port 1 and an output port 8; a first zone 3 of solids settling from wastewater below the level of the inlet port 1; a second zone 7 of solids settling below the level of the output port 8; and a compartment 14, such that the first sedimentation zone 3 is in communication with the compartment 14 and said compartment 14 is in communication with the second sedimentation zone 7. Biological contact rotor 4 is mounted to rotate in the compartment 14. In this patent, both anaerobic and aerobic processes for wastewater treatment are executed; like the earlier patent, it is not disclosed or suggested an additional separator of the purely anaerobic zone, or a biogas recovery system that allows to collect and recover the gas for reuse; nor disclosed or suggested a scum collection system or sludge collecting from the additional transition zone. The design and configuration of the tank, does not allow a continuous and efficient process of wastewater sanitation.
In Mexico was found the patent application MX/a/2007/013635 to Leticia Montoya Herrera et al. filed on Oct. 31, 2008, which discloses a purification apparatus for wastewater treatment from agribusiness called duplex anaerobic reactor consisting of two similar tanks connected in series. Each tank has attached at the upper part a truncated conical part with 60° angled walls. This has an inverted hood with 60° walls, called biogas separation chamber, including at least one scum collection and dislodge hood outside each tank by means of a pipe.
It also has a circular distributor, formed of evenly distributed sections, each section is attached by one or more tubes that descend fastened to the bottom of the tank. At the upper part each tank has a sedimentation chamber for separation of treated water and sludge, and attached to it a peripheral sink which in turn has an annular collector channel of treated water with at least one pipe which connects the two tanks to provide the wastewater feed into the second tank distributor for further treatment. With this duplex anaerobic reactor, efficiencies of at least 80% of removal are obtained in wastewater treatment from agribusiness with OCD values greater than 5000 mg/l.
Also is cited as reference the patent applications MX/a/2011/004708 and MX/a/2008/008724.
Was not found in any of the above mentioned documents, a combined bioreactor for wastewater treatment by means of anaerobic, aerobic and anoxic processes of degradation of organic matter which integrally comprises a collection system of biogas, scum and sludge in a practical, efficient and functional manner, and in the same reservoir allows the execution of anaerobic, aerobic and anoxic digestion with the possibility of sanitize wastewater, achieving a removal efficiency of OBD (oxygen biological demand) and TSS (total suspended solids) greater than 95%, besides a nitrification process. Where the collected biogas can be used as fuel to preheat the input current or as feedstock for cogeneration of energy that can be used in the process in the same plant or for any other purpose.